2. Then add excessive BaCl? Solution, get rid of Na? SO4:BaCl？ +Na？ So what? = = Basso? ↓+2NaCl
3. Then add excess NaOH solution to remove MgCl? :MgCl？ +2NaOH==Mg(OH)？ ↓+2NaCl
4. then add excessive Na? CO？ Solution, remove CaCl? And BaCl? (two reaction equations): Na? CO？ +CaCl？ ==CaCO？ ↓+2 NaCl； Na？ CO？ +BaCl？ ==BaCO？ ↓+2NaCl
5. Finally, drop an appropriate amount of hydrochloric acid until no gas is generated, and remove NaOH and Na? CO？ (PH test paper can detect pH, and there are also two reaction equations): HCl+NaOH==NaCl+H? o； 2HCl+Na？ CO？ ==2NaCl+H？ O+CO？ ↑
6. Evaporating the solution to precipitate NaCl crystals.
Does the crude salt contain insoluble impurities such as precipitate and soluble impurities such as Ca2+ and Mg2+? 2-? Wait a minute. Insoluble impurities can be removed by filtration, while soluble impurities such as Ca2+, Mg2+ and SO42- can be removed by adding BaCl? , NaOH and Na? CO？ Solution is removed by precipitation, BaCO? Solid and sodium hydroxide solution are removed. Then the water is evaporated to obtain pure refined salt.
Extended data:
Instrument:
Drugs: crude salt, distilled water, BaCl? Solution, NaOH solution, Na? CO？ Solution, hydrochloric acid.
Equipment: tray balance (including weight), measuring cylinder, beaker, glass rod, medicine spoon, funnel, filter paper, iron shelf (with iron ring), evaporating dish, alcohol lamp, crucible pliers, rubber-tipped dropper, mortar, pestle, matches and several small pieces of paper.
Pay attention to one post, two lows and three inclines when filtering.
① "One stick" means that the folding angle of the filter paper should be consistent with the diameter of the inner wall of the funnel, so that the wet filter paper can cling to the inner wall of the funnel without bubbles, because if there are bubbles, it will affect the filtration speed.
② "Two lows" means that the edge of the filter paper is slightly lower than the edge of the funnel, and the filtrate level should always be lower than the edge of the filter paper during the whole filtration process. This can prevent impurities from directly flowing into the beaker without filtration, so that the unfiltered liquid is mixed with the filtrate, which makes the filtrate turbid and fails to achieve the purpose of filtration.
③ "Three-way" means that when the liquid to be filtered is poured into the funnel, the beaker mouth of the beaker containing the liquid to be filtered should lean against the inclined glass rod (glass rod drainage) to prevent the liquid from splashing and the liquid to be filtered from breaking through the filter paper; Second, the lower end of the glass rod should gently lean against the three-layer filter paper to prevent it from breaking (one side of the three-layer filter paper is thicker than the other, and the three-layer filter paper is not easy to break); Thirdly, the neck of the funnel should be close to the inner wall of the receiver that receives the filtrate to prevent the liquid from splashing out.
References:
Baidu Encyclopedia-Purification of Crude Salt